Biology subjects

Tasaki, E.

Publications and source records attributed to Tasaki, E..

3 recordsLinked to original sources

bioRxiv2023

Cell type specific polyploidization in the royal fat body of termite queens

Tissue-specific endopolyploidy is widespread among plants and animals and its role in organ development and function has long been investigated. In insects, the fat body cells of sexually mature females produce substantial amounts of egg yolk precursor proteins (vitellogenins) and exhibit high polyploid levels, which is considered crucial for boosting egg production. Termites are social insects with a reproductive division of labor, and the fat bodies of mature termite queens exhibit higher ploidy levels than those of other females. The fat bodies of mature termite queens are known to be histologically and cytologically specialized in protein synthesis. However, the relationship between such modifications and polyploidization remains unknown. In this study, we investigated the relationship among cell type, queen maturation, and ploidy levels in the fat body of the termite Reticulitermes speratus. We first confirmed that the termite fat body consists of two types of cells, that is, adipocytes, metabolically active cells, and urocytes, urate- storing cells. Our ploidy analysis using flow cytometry has shown that the fat bodies of actively reproducing queens had more polyploid cells than those of newly emerged and pre-reproductive queens, regardless of the queen phenotype (adult or neotenic type). Using image-based analysis, we found that adipocytes became polyploid during queen differentiation and subsequent sexual maturation. These results suggest that polyploidization in the termite queen fat body is associated with sexual maturation and is regulated in a cell type-specific manner. Our study findings have provided novel insights into the development of insect fat bodies and provide a basis for future studies to understand the functional importance of polyploidy in the fat bodies of termite queens.

zoology↗

bioRxiv2022

King- and queen-specific degradation of uric acid is the key to reproduction in termites

Caste-based reproductive division of labour in social insects is built on asymmetries in resource allocation within colonies. Kings and queens dominantly consume limited resources for reproduction, while non-reproductive castes such as workers and soldiers help reproductive castes. Studying the regulation of such asymmetries in resource allocation is crucial for understanding the maintenance of sociality in insects, although the molecular background is poorly understood. We focused on uric acid, which is reserved and utilized as a valuable nitrogen source in wood-eating termites. We found that king- and queen-specific degradation of uric acid is the key to reproduction in the subterranean termite Reticulitermes speratus. The urate oxidase gene (RsUAOX), which catalyses the first step of nitrogen recycling from stored uric acid, was highly expressed in mature kings and queens, and upregulated with differentiation into neotenic kings/queens. Suppression of uric acid degradation decreased the number of eggs laid per queen. Uric acid was shown to be provided by workers to reproductive castes. Our results suggest that the capacity to use nitrogen, which is essential for the protein synthesis required for reproduction, contributes to colony cohesion expressed as the reproductive monopoly held by kings and queens.

ecology↗

bioRxiv2022

Seasonal movement of royal chambers: where are the kings and queens of temperate termites in winter?

Overwintering is a critical part of the annual cycle for species that live in temperate, polar, and alpine regions. As a result, low-temperature biology is a key determinant of temperate species distribution. Termites distribute predominantly in tropical regions, and only a few species are found in the temperate zone. As with other social insects, termites are characterized by the division of labor between reproductive and non-reproductive castes in which the survival of reproductives is crucial to maintaining their society. Here, in the termite Reticulitermes speratus, we report the discovery of an underground royal chamber that kings and queens use to survive the winter, which is separate from the one they use during the warmer breeding season. Our investigation of field colonies indicates that in the spring the royals are localized in decayed logs on the ground, then move to their underground royal chamber located in the roots of stumps in the fall. The winter minimum temperature measured in the royal chamber was higher than the ground surface temperature. In overwintering termites, the kings and queens had higher cold tolerance than workers and soldiers. The kings and queens were at risk of mortality from -8 {degrees}C, compared to the workers and soldiers at -4 {degrees}C. Air temperatures dropped below this critical temperature of -8 {degrees}C multiple times, as evidenced from the past 140 years of weather records in Kyoto. This suggests that the underground movement of the royal chamber may contribute to avoiding the risk of overwintering mortality. These results demonstrate the social strategies implemented to overcome the environment met while living at the latitudinal limits. This study sheds light on one of the most important aspects of the biology of termites in terms of predicting their geographic distribution and spread by climate change. This work also helps further the understanding of the termites social system, seasonal phenology, long-term survivorship, and life cycle, and contributes to the development of pest control strategies.

ecology↗